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[Bryan Derksen]

So I've built the giant stack of magma pumps with which to raise the magma ocean to the accursed surface, a marvel of carefully-isolated engineering that cannot possibly go awry or allow sneaky fire-immune creatures to sneak into my fort. I want to power it with a similarly self-contained power source that's impervious to outside attack. To that end I dug out a chamber to hold 8 water wheels, connecting it to a cavern lake via carved fortifications and a drain to a lower cavern level via a similar carved fortification. But when I open the floodgates the water does nothing. As the waterwheel channel filled I got a few sporadic readings of 100 or 300 power units being generated, way below the total theoretical capacity of the water wheels and not nearly enough to start the pump system moving. Once the channel had finished filling the power output dropped to 0 and remained there indefinitely.

I've tried running the water at various depths, and I've tried dismantling the whole thing and digging down a level lower to put pressurized water under the wheels. Magmawiki says that whether a tile of water has "flow" or not is complicated but doesn't go into detail about what the complications actually are. Does anyone have experience with these matters to suggest how I might fix my power station? This map has no brook or aquifer, just two cavern layers with a water supply and a bottom cavern layer with none.

[Xenos]

What I would recommend you do is make a water reactor unless you have a stream.

[slothen]

Reactor would be best, but you might want to try some science of your own.  Have the lake fill a channel that you dig with the water wheels, but have the other end drain down a few z-levels somewhere, say off a channeled map edge a z-level down.  Then water will flow under your wheels, creating power.  also, use a diagonal bend to kill pressure from the intake to reduce fun.  The reduced pressure will also more reliably generate 'flow' because water will teleport across 7/7 water tiles, and you want 4/7-6/7 actually get it moving under the wheels.

[beekay]

Flow, as far as I'm aware, can be present in two cases. The first is if units of water are diffusing from one tile to an adjacent tile (i.e. 6/7 spreads to 3/7,3/7). The water is considered to be flowing in that case. However, once you're dealing with a channel of 7/7 water, the pump starts teleporting new water directly to the end, and there's no actual movement within the channel. The only other way to generate flow is to have a river or brook on your map, since these carry a "Flowing" tag.

As such, ether you'll need to set up a system where water constantly diffuses across below a waterwheel, or you'll need to create a water reactor. The water reactor is the only really workable way to provide power, in my opinion.

[slothen]

just to reiterate, the diagonal bend that kills pressure always prevents water from teleporting across the wheel via pump, so long as there is sufficient drainage.

[Bryan Derksen]

Alright. Since the laws of physics didn't work correctly when I tried to play nice with them, I'll punish the laws of physics. Water reactors it is.

[oris472]

You could create a reservoir with pumps that pump the water out into your waterwheel-lined channel.  Place pumps at the end of the channel that feed water back into the reservoir, either directly or via a larger fort-wide plumbing system.  Use dwarfpower to give it the initial "push" and it will run self-sufficiently for quite a while.  Extra waterwheels will decrease the chances of the system getting stuck and requiring a manual restart.

[Shoku]

I think with a system like yours you would have been best off by having the fortification, wheels, and then a pump that fed water into a long channel that dropped it back into the water. As people have said water can teleport past pumps but it probably wouldn't stop all the flow like this and if it did you could either pipe the water into a different body of water or install one of those diagonals before the pumps.

[Bryan Derksen]

I already tried systems like those (well, they didn't have a pump feeding them, but at that point thermodynamics goes out the window anyway so I might as well skip that and go to the water reactors). The "sweet spot" of water depth was too narrow for all of my waterwheels to receive power at the same time. Oh well.

Anywho, I walled the architect of my old power station up with his failure and dug out a new site for a parallel array of five dual-wheel reciprocating water reactors with top-mounted power taps. This is a nice-looking arrangement too, I must say. Rather than laboriously pail-fill the reservoirs of the reactors and manually priming them I decided to dig a temporary inlet in the ceiling and dump the cavern lake in from above. Turns out these things will run just fine even completely submerged under three Z levels of water. Dwarven engineering at its finest.

Oddly enough running the power station gave me a noticeable hit on FPS but the much larger magma pump stack didn't add to it. I guess that's the price one pays for pantsing the laws of thermodynamics.

[MagmaMcFry]

Wouldn't the water just teleport over? Why should there be flow?

[jfsh]

I had the same problem when I tried to make a "real" waterwheel setup.  Trying to figure out why it wasn't working right drove me crazy.  The water reactor is the best choice for now, I think (and as you point out, it looks sharp!).